The present invention relates to a bicycle cycle computer for displaying various kinds of information regarding the speed, the pedal revolution per minute (rpm), the gear in operation, the pulse of the rider, the ambient temperature, the geographical height and the like.
Generally speaking, since a bicycle cycle computer is mounted on a bicycle and mainly used outdoors, it is required to be not only compact but also waterproof, shockproof and weatherproof. As shown in FIG. 1, a conventional, commercially available bicycle cycle computer comprises a main unit 10, and a display 20 for displaying data, such as the is speed, the distance traveled, the time and the pedal rpm, is provided on the front surface of the main unit 10. A mode button 12 for selecting different displaying modes is provided below the display 20. FIG. 2 shows the back of the main unit 10. In FIG. 2, reference numeral 13 denotes a battery cap for covering a battery accommodating chamber, 14 denotes a set button for switching among different data setting modes, 15 and 16 denote metal contacts for transmitting respective signals representing the detected speed and the detected pedal rpm (which will be described later) to a microprocessor (not shown) installed inside the main unit 10, and 17 denotes a metal contact as a common ground.
In addition, in order to prevent the main unit 10 from being stolen, the main unit 10 is preferably made to be detachable from the bicycle and portable. For this purpose, a conventional cycle computer is usually equipped with a bracket 30, as shown in FIG. 3, which is mounted on a handlebar 90 of a bicycle by means of a screw 31. The main unit 10 can be inserted in the direction indicated by the arrow A as shown in FIG. 3 so as to be detachably mounted onto the bracket 30. Thus, the rider can easily remove the main unit 10 from the bracket 30 whenever the bicycle is not in use, and mount the main unit 10 again later.
FIG. 4 shows the connection between the bracket 30 as shown in FIG. 3 and two sensors 42 and 52 via cables 46 and 56. FIG. 5 shows the position relationship between a magnet 44 mounted on one spoke 92 of the front wheel and the sensor 42 of FIG. 4 mounted on the inside of the fork 94, facing the magnet 44, and FIG. 6 shows the position relationship between a magnet 54 mounted on the inside of the crank 95 and the sensor 52 of FIG. 4 mounted on the chain stay 96, facing the magnet 54.
Among various data which can be displayed on the display 20 of the main unit 10, except the time data which is provided by a clock circuit built in the main unit 10, all the other data including the speed, the distance, the pedal rpm, etc., are obtained from signals supplied by the sensors 42 and 52 mounted on the fork 94 and the chain stay 96, respectively. The sensors 42 and 52 detect the numbers of rotation of the front wheel and the pedal crank 95 by sensing the associated magnets 44 and 54. The sensors 42 and 52 transmit thus detected signals via the cables 46 and 56 to the bracket 30. The signals are then transmitted to the microprocessor (not shown) in the main unit 10 through metal contacts 35 and 36 provided on the bracket 30 which are in electrical connection with the contacts 15 and 16 on the back of the main unit 10 when the main unit 10 is mounted on the bracket 30. The microprocessor performs, for example, identification, counting and calculation, on the supplied wheel rpm and pedal rpm data, and the processed data are then displayed on the display 20.
For example, the microprocessor of the main unit 10 calculates the speed by multiplying the wheel rpm with the circumferential length of the front wheel and calculates the distance traveled based on the calculated speed. In addition, the current pedal rpm or the average pedal rpm can be displayed to facilitate the rider's adjustment.
Therefore, as far as the main unit 10 of a cycle computer having two sensors 42 and 52 as mentioned above is concerned, it is necessary to provide two contacts 15 and 16 for transmitting signals supplied from the two sensors, respectively, to the microprocessor in the main unit 10 and a contact 17 for a common ground. That is, it is necessary to provide at least three contacts on the back of the main unit. Each of these contacts 15, 16 and 17 has to be provided on the back of the main unit 10 with a waterproof arrangement in order to prevent water from leaking into the interior of the main unit 10 to thereby result in a short circuit phenomenon. A typical waterproof arrangement for the contact is shown in FIG. 7. Holes 15a, 16a and 17a are provided at the bottom of a lower case 1Oa of the main unit 10. Waterproof O-rings 15b, 16b and 17b are disposed in the holes 15a, 16a and 17a, respectively. Contact pins 15c, 16c and 17c are inserted to pass through the respective O-rings and protrude from the respective holes. Springs 15d, 16d and 17d for biasing the respective contact pins 15c, 16c and 17c outwards are provided between the pins and the printed circuit board 102. It is apparent that the waterproof arrangement for the contact is relatively complicated and the manufacturing cost therefore is high.
Recently, following the development of the handlebar-type gear shifting device and the electronic gear shifting device, there is a demand for a new generation cycle computer which in addition to display the aforementioned data concerning the speed, the distance, the time and the pedal rpm, is also capable of displaying data concerning the gear in operation, the torque exerted on the crank shaft, the ambient temperature, the geographical height and even the pulse of the rider. This means a significant increase in the number of the sensors and hence the metal contacts on the back of the main unit and the corresponding metal contacts on the bracket. Due to the significantly increased number of the metal contacts, it is difficult to keep the main unit compact. In addition, it is necessary to provide a waterproof arrangement for each of the contacts, thereby resulting in a very complicated structure and an increased manufacturing cost.